JP7708084B2 - Vehicle underbody structure - Google Patents

Description

The present invention relates to a vehicle undercarriage.

In a vehicle in which a battery case containing a battery is mounted below a cross member, a structure is known in which the seat bracket rotates to deform the outer end of the cross member in the vehicle width direction downward in the event of a side collision, thereby absorbing the collision load (see, for example, Patent Document 1).

JP 2021-113006 A

However, in the above structure, the cross member must be positioned in the fore-and-aft direction of the vehicle at the same position as the rear portion of the seat bracket that supports the front seat. In other words, the cross member must be positioned close to the rear seat. In this case, the toes of passengers sitting in the rear seat will hit the cross member through the floor panel, resulting in a problem of narrowing the foot space for passengers sitting in the rear seat.

Therefore, the present invention aims to provide a vehicle underbody structure that can absorb collision loads during a side collision without narrowing the legroom of passengers seated in the rear seats.

In order to achieve the above object, the vehicle underbody structure according to the first aspect of the present invention comprises a battery case mounted on the vehicle underside of a floor panel of the vehicle, a cross member extending in the vehicle width direction between the floor panel and the battery case and further forward than the rear portion of a support member supporting the front seat of the vehicle, a rocker extending in the vehicle front-rear direction on the vehicle width outer side of the cross member, and a connecting member formed in a closed cross-sectional shape and connecting the vehicle width outer end of the cross member to the rocker, and a first weak part and a second weak part extending in the vehicle front-rear direction from the outermost part to the inner part in the vehicle width direction are formed on the upper wall of the connecting member, and a third weak part extending in the vehicle front-rear direction is formed on the lower wall of the connecting member between the first weak part and the second weak part in a front view, and the distance in the vehicle width direction between the first weak part and the third weak part is shorter than the distance in the vehicle width direction between the second weak part and the third weak part.

According to the first aspect of the invention, in the event of a side collision of the vehicle, a collision load directed toward the inside in the vehicle width direction is input to the connecting member via the rocker. Here, a first weak portion and a second weak portion extending in the vehicle front-rear direction are formed in the upper wall of the connecting member in order from the outermost side to the inside in the vehicle width direction, and a third weak portion extending in the vehicle front-rear direction is formed in the lower wall of the connecting member between the first weak portion and the second weak portion in a front view. The distance in the vehicle width direction between the first weak portion and the third weak portion is shorter than the distance in the vehicle width direction between the second weak portion and the third weak portion.

Therefore, when a collision load directed toward the inside in the vehicle width direction is input to the connecting member, the upper and lower walls of the connecting member between the first and second weak parts are deformed so as to convex toward the upper side of the vehicle. This makes it possible to deform the outer end in the vehicle width direction of the cross member, which extends in the vehicle width direction forward of the rear part of the support member that supports the front seats of the vehicle, toward the lower side of the vehicle, and to deform the approximate center part in the vehicle width direction of the cross member toward the upper side of the vehicle. In other words, the connecting member and the cross member absorb the collision load during a side collision of the vehicle without narrowing the foot space of the occupants sitting in the rear seats.

The second aspect of the vehicle underbody structure according to the present invention is the first aspect of the vehicle underbody structure, in which the third weak part is formed to be weaker than the first weak part and the second weak part.

According to the second aspect of the invention, the third weak portion is formed to be weaker than the first weak portion and the second weak portion. Therefore, when a collision load toward the inside of the vehicle width direction is input to the connecting member during a side collision of the vehicle, the upper and lower walls of the connecting member between the first and second weak portions are easily deformed so as to be convex toward the upper side of the vehicle.

The vehicle underbody structure of the third aspect of the present invention is the vehicle underbody structure of the first aspect, in which the first weak portion, the second weak portion, and the third weak portion are respectively a first bead portion, a second bead portion, and a third bead portion, and the depth of the third bead portion is deeper than the depths of the first bead portion and the second bead portion.

According to the third aspect of the invention, the first weak portion, the second weak portion, and the third weak portion are the first bead portion, the second bead portion, and the third bead portion, respectively, and the depth of the third bead portion is made deeper than the depth of the first bead portion and the second bead portion. Therefore, when a collision load toward the inside in the vehicle width direction is input to the connecting member during a side collision of the vehicle, the upper and lower walls of the connecting member between the first weak portion (first bead portion) and the second weak portion (second bead portion) are easily deformed so as to be convex toward the upper side of the vehicle.

The fourth aspect of the vehicle underbody structure according to the present invention is the vehicle underbody structure according to any one of the first to third aspects, in which the connecting member has a lower rigidity than the cross member.

According to the fourth aspect of the invention, the connecting member has a lower rigidity than the cross member. Therefore, when a collision load toward the inside of the vehicle width direction is input to the connecting member, the upper and lower walls of the connecting member between the first and second weak parts are more likely to deform so as to become convex toward the upper side of the vehicle.

As described above, the present invention can absorb the collision load during a side collision of the vehicle without narrowing the legroom of passengers seated in the rear seats.

1 is a schematic front view showing a vehicle underbody structure according to an embodiment of the present invention; 1 is a schematic plan view showing a vehicle underbody structure according to an embodiment of the present invention; 2 is an enlarged schematic front view showing the vehicle lower structure according to the embodiment before a side collision; FIG. 2 is an enlarged schematic front view showing the vehicle lower structure according to the embodiment after a side collision; FIG. 5A to 5C are schematic diagrams showing the deformation process of the extension and cross member in this embodiment during a side collision.

The following is a detailed description of an embodiment of the present invention with reference to the drawings. For ease of explanation, the arrow UP shown in each drawing indicates the upward direction of the vehicle, the arrow FR indicates the forward direction of the vehicle, the arrow LH indicates the leftward direction of the vehicle, and the arrow RH indicates the rightward direction of the vehicle. In the following description, unless otherwise specified, the upward, downward, forward, backward, leftward, and rightward directions refer to the upward, downward, forward, backward, and leftward directions of the vehicle. The leftward and rightward directions are synonymous with the vehicle width direction.

As shown in Figures 1 and 2, a vehicle 12 to which the vehicle undercarriage structure 10 according to this embodiment is applied includes a frame member 15 that is substantially rectangular in shape and is disposed between the axles of the front wheels Fw (not shown) and the axles of the rear wheels Rw (not shown) in a plan view. A floor panel 14 that constitutes the floor of the vehicle 12 is disposed above the frame member 15, and a battery case 16 is mounted below the frame member 15.

That is, the frame member 15 is disposed between the floor panel 14 and the battery case 16 when viewed from the front. Although the floor panel 14 and the battery case 16 are not shown in FIG. 2, the battery case 16 is supported by the frame member 15 and the like. Also, as shown in FIG. 1, the inside of the battery case 16 houses a battery stack 17, which is made up of multiple battery cells 17A stacked in the front-rear direction and arranged in multiple rows in the vehicle width direction. In other words, the vehicle 12 is an electric vehicle or a plug-in hybrid vehicle.

The frame member 15 has a metallic cross member 20 extending in the vehicle width direction, and a pair of metallic left and right rockers 30 extending in the front-rear direction on the outer side of the cross member 20 in the vehicle width direction. The cross member 20 has a generally hat-shaped cross section and is provided in the approximate center of the frame member 15 in the front-rear direction (see FIG. 2). Note that the frame member 15 also has cross members (not shown) similar to the cross member 20 provided on the front and rear sides of the cross member 20.

As shown in FIG. 2, the vehicle 12 (cross members, side members, etc., not shown) is provided with seat brackets 18 as a pair of front and rear support members to which the front and rear lower parts of seat rails (not shown) that slidably support the front seat (not shown) are attached (only the seat bracket 18 on the outer side in the vehicle width direction is shown in FIG. 2). The cross member 20 is disposed forward of the rear part 18B of the seat bracket 18 and rearward of the front part 18F of the seat bracket 18 in a plan view.

The frame member 15 also has a metal extension 22 that serves as a connecting member that connects the outer end of the cross member 20 in the vehicle width direction to the rocker 30. The extension 22 has a lower rigidity than the cross member 20. In other words, the plate thickness of the extension 22 is formed to be thinner than the plate thickness of the cross member 20. Other configurations of the extension 22 will be described in detail later.

1 and 2, the rocker 30 has a rocker outer panel 32 that is formed with a generally hat-shaped cross section and extends in the front-to-rear direction, and a rocker inner panel 34 that is formed with a generally hat-shaped cross section and extends in the front-to-rear direction. The rocker 30 is formed into a closed cross-sectional shape by joining the upper and lower flange portions 32A of the rocker outer panel 32 and the upper and lower flange portions 34A of the rocker inner panel 34 to each other by welding or the like.

The extension 22 is formed with a closed cross-sectional shape (a square tube with a substantially rectangular cross-section) in a side view, and its inner end in the vehicle width direction is inserted into the inside of the outer end in the vehicle width direction of the cross member 20 and joined integrally by welding or the like. A flange portion (not shown) is integrally formed on the outer end in the vehicle width direction of the extension 22 (at least the outer end in the vehicle width direction of the upper wall 22U), and the flange portion is joined to the rocker 30 (rocker inner panel 34) by welding or the like.

As shown in FIG. 3, the upper wall 22U of the extension 22 is provided with a first bead portion 24 as a first weak portion extending in the front-rear direction and recessed downward in a generally arc-shaped cross section, and a second bead portion 26 as a second weak portion extending in the front-rear direction and recessed downward in a generally arc-shaped cross section, which are formed in that order from the outermost side to the inner side in the vehicle width direction.

That is, the first bead portion 24 is formed on the outermost side in the vehicle width direction on the upper wall 22U of the extension 22, and the second bead portion 26 is formed on the inner side in the vehicle width direction of the first bead portion 24 with a predetermined space therebetween. Then, the third bead portion 28 is formed as a third weak portion that is recessed upward in a cross-sectionally approximately arc-shaped manner and extends in the front-rear direction on the lower wall 22D of the extension 22 between the first bead portion 24 and the second bead portion 26 in the front view shown in FIG. 3.

As shown in FIG. 3, the distance D1 between the first bead portion 24 and the third bead portion 28 in the vehicle width direction is shorter than the distance D2 between the second bead portion 26 and the third bead portion 28 in the vehicle width direction. The third bead portion 28 is also formed to be weaker than the first bead portion 24 and the second bead portion 26. In other words, the depth (amount of recess) of the third bead portion 28 is deeper (larger) than the depth (amount of recess) of the first bead portion 24 and the second bead portion 26.

The operation of the vehicle underbody structure 10 according to this embodiment, which is configured as described above, will now be described.

When the vehicle 12 collides sideways with a barrier W (see FIG. 5) such as a pole, a collision load is input from the outside in the vehicle width direction to the inside in the vehicle width direction through the rocker 30 to the extension 22. Here, as shown in FIG. 3, a first bead portion 24 and a second bead portion 26 extending in the front-rear direction are formed in the upper wall 22U of the extension 22 in order from the outermost side to the inside in the vehicle width direction, and a third bead portion 28 extending in the front-rear direction is formed on the lower wall 22D of the extension 22 between the first bead portion 24 and the second bead portion 26 in a front view.

The distance D1 between the first bead portion 24 and the third bead portion 28 in the vehicle width direction is shorter than the distance D2 between the second bead portion 26 and the third bead portion 28 in the vehicle width direction. Therefore, when a collision load toward the inside of the vehicle width direction is input to the extension 22, as shown in FIG. 4, the upper wall 22U and the lower wall 22D of the extension 22 between the first bead portion 24 and the second bead portion 26 are plastically deformed so as to be convex upward.

To explain more specifically, as shown in FIG. 5(A), when the vehicle 12 collides sideways with the barrier W, a collision load is input relatively from the barrier W to the rocker 30. When a collision load is input to the rocker 30 from the outside in the vehicle width direction, as shown in FIG. 5(B), the rocker 30 collapses toward the inside in the vehicle width direction, absorbing part of the collision load, and the remaining part of the collision load is transmitted to the extension 22.

When a collision load is input to the extension 22 from the outside in the vehicle width direction, as shown in FIG. 5(C), the extension 22 plastically deforms so as to bend with the first bead portion 24, the third bead portion 28, and the second bead portion 26 as base points, absorbing the collision load. In other words, the upper wall 22U and the lower wall 22D of the extension 22 between the first bead portion 24 and the second bead portion 26 plastically deform so as to become convex upward, absorbing the collision load.

This allows the outer end of the cross member 20 in the vehicle width direction (the boundary between the cross member 20 and the extension 22) to deform downward (so as to become convex downward), and allows the approximate center of the cross member 20 in the vehicle width direction to deform upward (so as to become convex upward) (see Figure 5 (C)).

The cross member 20 extends in the vehicle width direction forward of the rear portion 18B of the seat bracket 18 that supports the front seat of the vehicle 12 (specifically, the rear lower portion of the seat rail that slidably supports the front seat), so that the toes of an occupant sitting in the rear seat do not hit the cross member 20 through the floor panel 14.

Therefore, the extension 22 and the cross member 20 can efficiently absorb the collision load during a side collision of the vehicle 12 without narrowing the legroom of the passengers seated in the rear seats. This also makes it possible to suppress or prevent the cross member 20 and the barrier W from hitting the battery case 16, thereby effectively suppressing or preventing the collision load from being input to the battery stack 17 via the battery case 16.

The third bead portion 28 formed on the lower wall 22D of the extension 22 is formed to be weaker than the first bead portion 24 and the second bead portion 26 formed on the upper wall 22U of the extension 22. Specifically, as shown in FIG. 3, the depth (recess amount) of the third bead portion 28 is deeper (larger) than the depth (recess amount) of the first bead portion 24 and the second bead portion 26.

Therefore, when a collision load toward the inside of the vehicle width direction is input to the extension 22 during a side collision of the vehicle 12, the upper wall 22U and the lower wall 22D of the extension 22 between the first bead portion 24 and the second bead portion 26 can be easily deformed so as to be convex upward. In other words, the upper wall 22U and the lower wall 22D of the extension 22 between the first bead portion 24 and the second bead portion 26 can be effectively induced (controlled) to deform convexly upward.

As described above, since the flange portion integrally formed at least on the outer end in the vehicle width direction of the upper wall 22U of the extension 22 is joined to the rocker 30, when a collision load is input to the extension 22 via the rocker 30, the collision load is likely to be transmitted mainly from approximately the center in the height direction of the extension 22 to the upper side. Therefore, even if a deep third bead portion 28 (large recess amount) is formed on the lower wall 22D of the extension 22, it is possible to suppress a decrease in the strength of the extension 22 against the collision load, and a decrease in the energy absorption efficiency of the extension 22 can be suppressed.

Furthermore, the extension 22 has a lower rigidity than the cross member 20. Specifically, the plate thickness of the extension 22 is formed to be thinner than the plate thickness of the cross member 20. Therefore, when a collision load toward the inside of the vehicle width direction is input to the extension 22, the upper wall 22U and the lower wall 22D of the extension 22 between the first bead portion 24 and the second bead portion 26 can be deformed more easily so as to be convex upward.

The vehicle underbody structure 10 according to this embodiment has been described above with reference to the drawings, but the vehicle underbody structure 10 according to this embodiment is not limited to the one shown in the drawings, and the design can be modified as appropriate within the scope of the gist of the present invention. For example, the bead portions as weak parts formed in the extension 22 are not limited to the three shown in the drawings.

The extension 22 may have additional bead portions depending on its length along the vehicle width direction. That is, one or more bead portions similar to the first bead portion 24 or the second bead portion 26 may be formed on the upper wall 22U of the extension 22, on the inner side of the second bead portion 26 in the vehicle width direction, and one or more bead portions similar to the third bead portion 28 may be formed on the lower wall 22D of the extension 22, on the inner side of the second bead portion 26 in the vehicle width direction.

When the length of the extension 22 in the vehicle width direction is increased and bead portions are added to the upper wall 22U and the lower wall 22D, the added upper and lower bead portions do not have to be formed at the same position in the vehicle width direction. In other words, the added bead portions do not have to have a relationship such as the distance D1 between the first bead portion 24 and the third bead portion 28 and the distance D2 between the second bead portion 26 and the third bead portion 28. Therefore, the added bead portions may be formed, for example, alternating up and down at equal intervals in the vehicle width direction.

The first, second, and third weak portions are not limited to the first bead portion 24, second bead portion 26, and third bead portion 28 shown in the figure, and may be, for example, a first long hole portion, a second long hole portion, and a third long hole portion that are slit-shaped and long in the front-rear direction (not shown). In this case, if the opening area of the third long hole portion is made larger than the opening areas of the first and second long hole portions, the third long hole portion can be made weaker than the first and second long hole portions.

The configuration for making the rigidity of the extension 22 lower than that of the cross member 20 is not limited to being based on differences in plate thickness. For example, the metal material for forming the extension 22 may be a metal material with a lower rigidity than the metal material for forming the cross member 20, so that the rigidity of the extension 22 is lower than that of the cross member 20.

10 Vehicle underbody structure 12 Vehicle 14 Floor panel 16 Battery case 18 Seat bracket (support member)
20 Cross member 22 Extension (connecting member)
22U Upper wall 22D Lower wall 24 First bead portion (first weak portion)
26 Second bead portion (second weak portion)
28 third bead portion (third weak portion)
30 Rocker D1 Distance D2 Distance

Claims (4)

A battery case mounted on a vehicle lower side of a floor panel of the vehicle;
a cross member extending in a vehicle width direction between the floor panel and the battery case and further forward than a rear portion of a support member supporting a front seat of the vehicle;
a rocker extending in a vehicle front-rear direction on an outer side of the cross member in a vehicle width direction;
A connecting member formed in a closed cross-sectional shape and connecting an outer end portion of the cross member in the vehicle width direction to the rocker;
Equipped with
A first weak portion and a second weak portion are formed in the upper wall of the connecting member, the first weak portion and the second weak portion extending in the vehicle front-rear direction in this order from the outermost side to the inner side in the vehicle width direction, and a third weak portion is formed in the lower wall of the connecting member between the first weak portion and the second weak portion in a front view, the third weak portion extending in the vehicle front-rear direction,
A vehicle underbody structure, wherein a distance between the first weak portion and the third weak portion along a vehicle width direction is shorter than a distance between the second weak portion and the third weak portion along the vehicle width direction. The vehicle underbody structure according to claim 1, wherein the third weak portion is formed to be weaker than the first weak portion and the second weak portion. The vehicle underbody structure according to claim 1, wherein the first weak portion, the second weak portion, and the third weak portion are respectively a first bead portion, a second bead portion, and a third bead portion, and the depth of the third bead portion is deeper than the depths of the first bead portion and the second bead portion. The vehicle underbody structure according to any one of claims 1 to 3, wherein the connecting member has a lower rigidity than the cross member.